Cooling device

ABSTRACT

The invention relates to a cooling device for an electric energy supply ( 2 ), comprising at least one first heat-dissipating part ( 3 ), the power components ( 4 ) of which are connected to the cooling device ( 1 ) in a thermally conductive manner, wherein a fluid-conducting connection ( 5 ) conducts liquid coolant ( 6 ) from a pump ( 7 ) to a cooler ( 8 over the first heat-dissipating part ( 3 ), wherein one shut-off unit ( 9′, 9 ) each is arranged in the fluid-conducting connection ( 5 ) at least between the first heat-dissipating part ( 3 ) and the cooler ( 8 ) and between the pump ( 7 ) and the first heat-dissipating part ( 3 ). The cooling device is characterized in that, in order to avoid an overpressure in at least one part ( 3, 14 ) to be cooled, at least one pressure limiting valve ( 17, 28 ) is provided, which is arranged in connection with the fluid conductor inside the part ( 3, 14 ) and/or, as part of a unit ( 15 ) for preloading the cooling liquid ( 6 ) in the fluid-conducting connection ( 5 ), is connected to the part ( 3, 14 ) by means of the pressure sure side of a check valve ( 13 ) provided downstream of the part ( 3, 14 ).

The invention relates to a cooling device for an electric power supply comprising at least one first heat-dissipating part whose power components are connected to the cooling device in a thermally conductive manner, wherein a fluid-carrying conveys liquid coolant from a pump via the first heat-dissipating part to a cooler, there being one shutoff device at a time in the fluid-carrying connection of the cooling device at least between the first heat-dissipating part and the cooler and between the pump and the first heat-dissipating part.

Such a cooling device is disclosed in DE 2 135 677 A. The prior art cooling device is part of a transformer-rectifier device whose rectifier units are oil-cooled. The rectifier units are accommodated in separate rectifier housings, with the coolant or cooling oil being pumped by means of a pump through a pipeline and then in parallel through the rectifier units. After passing through and after cooling of the rectifier units, the heated coolant or cooling oil is returned to a cooler from where the coolant or cooling oil travels again to the pump. Near the inlet and outlet of each rectifier housing, there are valves which enable a separation of the individual housings from the pipeline.

Components of power electronics that require cooling are often used in the field of drive technology and electrical energy production. Thus, the use of converter modules in the drive technology of vehicles, such as, for example, streetcars, hybrid busses, or trolley busses which convert DC voltage into AC voltage and vice versa, is known.

In systems for producing electrical energy, such as in wind power plants, these converters are located in a housing module for electrical equipment. This housing module combines all feed lines of a generator up to a grid feed point. In addition, a transformer, a converter, and a cooling device can be combined as a unit in the housing. Such converters or rectifiers have a power transmission of several 1000 kW. Within a base body, there can be at least two modules which preferably comprise fast-switching power semiconductors, for example, IGBTs, and which can be made as prefabricated branch pair modules, such as a branch pair valve set. The heat which forms as a result of conversion losses, is dissipated to one or more cooling elements through or around which cooling liquid flows, often made as a water-glycol mixture for reasons of protecting against corrosion and freezing. Typically, a cooling liquid temperature of less than 70 degrees Celsius for the coolant entry should be maintained.

If work is to be performed on parts of this power electronic system for maintenance purposes, large amounts of cooling liquid may have to be removed from the cooling device. In particular, under constricted space conditions in systems such as the nacelle of a wind turbine, it is often hardly possible to set up suitable collection tanks for receiving the cooling liquid. Moreover, the complete removal of the cooling liquid from these systems is time-consuming.

Based on the indicated prior art, the object of the invention therefore is to devise a cooling device for the parts to be cooled which enables simple replacement of the parts to be cooled.

This object is achieved by a cooling device having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, to prevent an overpressure in at least one part which is to be cooled, there is at least one pressure limiting valve, which, in connection with the fluid duct, is located within the component and/or which, as part of a device for preloading the cooling liquid in the fluid-carrying connection, is connected to the component via the pressure side of a check valve provided downstream of the component. This precludes damage to the component, such as a converter, if during operation of the device the two cocks should be inadvertently closed, and an overpressure and bursting would be possible due to the temperature rise within the component. In a first alternative, there is a pressure limiting valve in connection with the fluid duct within the component; in a second alternative, an overpressure which may have built up in the component is relieved via the fluid-carrying connections toward the intake side of the pump whose pressure side in turn is connected to a pressure limiting valve for setting the system pressure.

If shutting-off of the fluid-carrying connection is enabled upstream and downstream of the cooling device for purposes of evacuating the coolant, in maintenance work only the relatively small volume of coolant need be drained from the region of the component to be maintained and need be removed from the cooling device. This reduces the time required for this draining process as well as the amount of space required for possible collection tanks of cooling liquid. A valve in the fluid-carrying connection between the two shutoff devices in the cooling device around the first heat-dissipating part enables the drainage of cooling liquid before repair of or maintenance on the heat-dissipating part of the electric power supply.

In one especially preferred exemplary embodiment, for each further heat-dissipating part of the electric power supply upstream and downstream on its cooling device and especially on the fluid-carrying connection of the pump and cooler which is provided for this purpose, there is a shutoff device with the indicated function and action. It can also be advantageous to arrange a pertinent shutoff device upstream and downstream of a node point in the fluid-carrying connection for coolants.

The shutoff device can be a valve of any form with a possible shutoff operating position, preferably in a seated valve design. It can be advantageous to use a shutoff valve of simple structure, for example, in the form of a cock for manual actuation. The operating position of the cock can be visually recognized from the outside in an economical design of the cooling device.

An automatic cutting-off of the fluid-carrying connection upstream and downstream of the heat-dissipating part of the power electronics of an electric power supply arises in the use of a check valve or a pilot-operated check valve. The latter is opened in the flow direction of the coolant flow downstream away from the heat-dissipating part and upstream toward the heat-dissipating part at a coolant pressure that is slightly above the atmospheric pressure. If the pump for coolant is turned off during a maintenance phase of the electric power supply and a pressure drop in the fluid-carrying connection is set to a boundary pressure, the check valve closes automatically upstream and downstream of the heat-dissipating part.

After the pump has been turned off, the pressure in the cooling device can, for example, be lowered by coolant being drained on an equalizing vessel for the cooling device.

In one especially preferred embodiment of the cooling device according to the invention, all heat-dissipating parts are located downstream of the high pressure side of the pump. In this way, before and after each heat-dissipating part, shutoff devices can be inserted into the fluid-carrying connection for coolant for the components and in a possible maintenance or repair of each heat-dissipating part for itself can be decoupled from the coolant circuit so that only the volume of coolant of the pertinent system component need be drained. This facilitates a restart of the system and prevents the risk of feeding air bubble or gas bubble inclusions into the coolant liquid; this otherwise could lead to “pulsation” of the pump and/or to cavitation phenomena in a restart.

In one exemplary embodiment of the cooling device, there is at least one heat-dissipating part in a converter which is preferably supported on a cooling element. In an electrical rectifier, electrical energy is converted into direct current in a 3-phase diode bridge circuit, as is generally recognized. Accordingly, a capacitor is used as a smoothing element for smoothing of the direct current. Then the electric current is transformed back by a frequency conversion in an inverter circuit with a transistor module and an IGBT module.

In the electrical converter, a conversion loss arises in the diode bridge, in the transistor module, and in the IGBT module, as well as in the reconversion elements, with heat being produced. The heat which forms is dissipated to a cooling element. In order to obtain a more or less constant operating pressure, there is preferably a device for preloading of the cooling liquid or of the liquid coolant in the cooling device. An accumulator which can be designed as a diaphragm accumulator, piston accumulator, or gas accumulator is used for this purpose. The liquid pressure in the accumulator is set by a pressure valve and is limited in this way. The cooling device according to the invention is especially suitable for wind power plants whose equipment and engine room on a mast make available limited space for maintenance personnel, tools, and devices or implements. Often, in the maintenance of components of these systems, only a few liters of cooling liquid need be drained after the shutoff devices have been closed upstream and downstream of the corresponding component or the heat-dissipating part.

The invention is detailed below using the drawings.

FIG. 1 shows a schematic circuit diagram of a first exemplary embodiment of the cooling device according to the invention, and

FIG. 2 shows a circuit diagram of another exemplary embodiment of the cooling device according to the invention.

FIG. 1 schematically shows in a schematic circuit diagram a cooling device I for an electric power supply 2 of a wind power plant with its essential components. The cooling device 1 is used to cool power components 4, such as a capacitor module with a filter and snubber capacitor and a semiconductor module of a converter 14. The converter 14 has a housing 18 with cooling plates 4 on which heat-dissipating parts 3 which are subject to loss are mounted. The cooling plates 4 are flushed by liquid coolant 6 which is preferably made as a water-glycol mixture. The operating temperature of the heat-dissipating parts 3 in the converter 14 is thus kept at temperatures at which self-destruction of the semiconductor elements is avoided.

The cooling device 1 has fluid-carrying connections 5 from a pump 7 to a cooler 8 in the form of tubes or hoses. The pump 7 is preferably made as a centrifugal pump and is driven by an electric motor 20 via a drive shaft 21. The pump 7 is furthermore designed preferably for a correspondingly large volumetric flow. The operating pressure of the cooling device 1 should be, for example, about 4 bar. In the fluid-carrying connection 5 upstream of the pump 7 at a nodal point 10, there is a connection to an accumulator 16 which forms a device 15 for preloading of the coolant 6 in the entire line network and for preloading for the connected cooling plates 4. There is a pressure valve 17 for setting the accumulator pressure.

Upstream of the nodal point 10, there is a shutoff device 9. The shutoff device 9 is made as cock 12. The cock 12 can be manually actuated and is preferably made as a ball valve. Upstream of the cock 12 is the converter 14 with cooling plates 4; this enables the heat of the parts 3 to be dissipated to the cooling medium which is flowing through the cooling plates 4. Upstream of the housing 18 of the converter 14, the fluid-carrying connection 5 is conveyed onward and has a second shutoff device 9′. FIG. 1 shows the second shutoff device 9′ as a manually actuated ball valve. In the exemplary embodiment shown in FIG. 2, instead of the ball cock, there is a shutoff valve 11 which is made as check valve 13. The check valve 13 blocks against a flow in the direction to the converter 14, but can be opened for a flow out of the converter 14 in a pressure-actuated manner.

The shutoff devices 9, 9′ enable a decoupling of the converter 14 from the remaining cooling system. A draining of coolant 6 from the cooling plates 4 of the converter 14, as described above, is easily enabled specifically in this way in order to expose the components of the converter 14 for maintenance purposes.

A nodal point 24 of a bypass line 25, which enables a coolant flow past a cooler 8 back to the pump 7, is mounted upstream of the second shutoff device 9′. The cooler 8, via which the coolant circulation normally takes place back to the pump 7, has a cooling fan which is driven by a motor 26 and which can be dimensioned such that it recools the coolant to a temperature that is suitable to make available sufficient heat storage capacity of the coolant for the heat-dissipating parts 3.

FIGS. 1 and 2 show only one exemplary application of the cooling device, in particular the incorporation of a heat-dissipating part 3 between the shutoff devices 9, 9′. Further heat-dissipating parts (not shown) can be similarly incorporated between the indicated shutoff devices 9, 9′ in the manner of a series connection.

As stated, in the example of FIG. 1, the shutoff devices 9, 9′ are designed as cutoff valves, for example, ball valves 12, upstream and downstream of the converter 14. In order to preclude damage of the converter 14, if both cocks were to be inadvertently closed during operation of the device, and an overpressure and bursting would be possible due to the temperature rise within the converter 14, in the example from FIG. 1, there is a pressure limiting valve 28 in connection with the fluid duct within the converter 14. As is apparent in the exemplary embodiment from FIG. 2, there is no pressure limiting valve on the converter 14 because the shutoff device 9′ provided downstream of the converter 14 is formed by a check valve 13 via which an overpressure, which may have built up in the converter 14, is relieved via the fluid-carrying connections 5, including the bypass line 25, toward the intake side of the pump 7, whose pressure side in turn is connected to the pressure limiting valve 17 for setting the system pressure via the nodal point 10. 

1. A cooling device for an electric power supply (2), comprising at least one first heat-dissipating part (3) whose power components (4) are connected to the cooling device (1) in a thermally conductive manner, wherein a fluid-carrying connection (5) conducts liquid coolant (6) from a pump (7) via the first heat-dissipating part (3) to a cooler (8), there being one shutoff device (9, 9′) at a time in the fluid-carrying connection (5) at least between the first heat-dissipating part (3) and the cooler (8) and between the pump (7) and the first heat-dissipating part (3), characterized in that to prevent an overpressure in at least one part (3, 14) which is to be cooled, there is at least one pressure limiting valve (17, 28) which in connection with the fluid duct is located within the component (3, 14) and/or which as part of a device (15) for preloading the cooling liquid (6) in the fluid-carrying connection (5) is connected to the component (3, 14) via the pressure side of a check valve (13) provided downstream of the component (3, 14).
 2. The cooling device according to claim 1, characterized in that there is one shutoff device (9, 9′) at a time upstream and downstream of each heat-dissipating part (3) of the electric power supply (2) between the heat-dissipating part (3) and a component located upstream and downstream in the latter or a nodal point (10) in the fluid-carrying connection (5).
 3. The cooling device according to claim 1, characterized in that at least one shutoff device (9) is formed from a cutoff valve (11).
 4. The cooling device according to claim 1, characterized in that at least one shutoff device (9) is designed as actuatable cock (12).
 5. The cooling device according to claim 1, characterized in that at least one shutoff device (9) is designed as a ball valve.
 6. The cooling device according to claim 2, characterized in that the cutoff valve (11) is a check valve (13) or a pilot-operated check valve which, viewed in the flow direction of the coolant flow, opens away from the heat-dissipating part (3) at the operating pressure of the cooling device (1).
 7. The cooling device according to claim 1, characterized in that all heat-dissipating parts (3) supplied by the cooling device (1) are located downstream of the pump (7).
 8. The cooling device according to claim 1, characterized in that at least the first heat-dissipating part (3) is a component of a converter (14).
 9. The cooling device according to claim 1, characterized in that the cooling liquid (6) is a water-glycol mixture.
 10. The cooling device according to claim 1, characterized in that the cooling device (1) has a device (15) for preloading of the cooling liquid (6) in the fluid-carrying connection (5).
 11. The cooling device according to claim 10, characterized in that the device (15) for preloading of the cooling liquid (6) comprises an accumulator (16).
 12. The cooling device according to claim 11, characterized in that the cooling liquid pressure in the system is limited by at least one pressure valve (17).
 13. The cooling device according to claim 1, characterized in that the cooling device (1) is part of a wind power plant.
 14. The cooling device according to claim 13, characterized in that the cooling device (1) is accommodated in a housing module of the wind power plant. 